This invention relates to an apparatus for mixing and spraying different colorants, i.e., paints, dyes and stains, to achieve various color combinations on a target workpiece. The invention is particulary applicable to application of camouflage paints on military vehicles, especially near the battlefront when it is desired to change the vehicle to match the color of the terrain or background scene.
This invention utilizes a pressurized air source to supply relatively constant pressure air to a venturi mixer system. Colorants are drawn into the venturi throat for thorough mixing and subsequent introduction to a spray nozzle. The throat of the venturi may be equipped with a relatively large number of suction ports equidistantly spaced around the throat circumference; e.g., eight suction ports. Each port is connected to a pipe or conduit that leads from a separate colorant supply vessel or container; a metering valve in each conduit regulates or varies the flow rate through the respective conduit. As pressurized air flows through the venturi throat, colorants are drawn through those ports that communicate with opened metering valves. The different colorants are intermixed with the pressurized air and each other in the venturi throat. By selective adjustment of the various metering valves, it is possible to produce a large range of colors, shades and hues from a relatively small number of primary colors.
Preferably, the colorant-mixing action is completed in an elongated cylindrical chamber connected to the exit end of the venturi throat. Rotating propellers or agitators within the chamber cooperate with fixed baffles on the chamber walls to achieve a complete colorant mixing action. The elongated chamber supplies the mixed colorant to a conventional spray gun.
In its preferred form, the invention includes additional features, such as colorant solvent distribution system for preventing clog-up of the system passages by partially dried colorant. Another advantageous feature involves a standby power means for operating the agitators in the cylindrical mixing chamber when there is no pressurized air flowing through the venturi. Use of the standby power source keeps the mixed colorants in a thoroughly mixed condition during short intervals between successive spray applications of the mixed colorant onto the work or target.
In order to achieve reproducible colors on the work with minimum trial-and-error experimentation, I contemplate that the controls for the individual metering valves will be correlated to provide a specific shade or hue from specific percentages of the pertinent primary colors, e.g., 3 parts white, 27 parts blue and 7 parts red. The individual metering valves can be individually adjusted in accordance with a color chart having the percentages of pertinent primary colors thereon. Alternately the individual metering valves can be interconnected at a master controller that can be set to automatically adjust the individual valves in accordance with a selected target color shown on the controller dial or on a separate color chart. If the metering valves are electrically operated, the valve flow rates can be selected by use of rheostats in the electrical valve control system. Direct manual setting of each valve is also possible .